| Date | November 2019 | Marks available | 3 | Reference code | 19N.3.sl.TZ0.15 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 15 | Adapted from | N/A |
Question
Codeine, morphine and diamorphine (heroin) are derived from opium.
State the names of two functional groups present in all three molecules, using section 37 of the data booklet.
Explain why diamorphine has greater potency than morphine.
Markscheme
Any two of:
benzene/aromatic ring ✔
«tertiary» amino «group» ✔
ethenylene/1,2-ethenediyl «group» ✔
ether «group» ✔
NOTE: Accept “phenyl” for “benzene ring” although there are no phenyl groups as the benzene ring in this compound is a part of a polycyclic structure.
Do not accept “arene” or “benzene” alone.
Accept “amine” for “amino «group»”.
Accept “alkenyl/alkene/vinylene” for ethenylene/1,2-ethenediyl «group».
Any three of:
morphine has «two» hydroxyl «groups» AND diamorphine has «two» ester/ethanoate/acetate «groups» ✔
NOTE: Accept “heroin” for “diamorphine”.
Accept formulas.
Accept “hydroxy” for “hydroxyl” but not “hydroxide”.
Accept “acyl” for “ester «groups»”.
morphine is more polar than diamorphine
OR
groups in morphine are replaced with less polar/non-polar groups in diamorphine ✔
NOTE: Do not accept just “diamorphine is non-polar” for M2.
morphine is «more» soluble in blood «plasma»
NOTE: Accept “water” for “blood”.
OR
diamorphine is «more» soluble in lipids
NOTE: Accept “fats” for “lipid”.
OR
diamorphine is more soluble in non-polar environment of CNS/central nervous system than morphine ✔
diamorphine crosses the blood–brain barrier/BBB «easily» ✔
